feat: init commit with main func

dns.go

@@ -0,0 +1,121 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"gopkg.in/yaml.v3"
+)
+
+// ZoneFile is the in-memory representation of a dynamic OctoDNS zone YAML file.
+// Keys are subdomain labels (empty string = apex record).
+// Values are either a single record map or a list of record maps (for multi-type).
+type ZoneFile map[string]interface{}
+
+// RecordStats counts the changes between two zone states.
+type RecordStats struct {
+	Added   int
+	Removed int
+	Changed int
+}
+
+// ReadZoneFile parses an OctoDNS YAML zone file.
+// If the file does not exist, returns an empty ZoneFile (not an error).
+func ReadZoneFile(path string) (ZoneFile, error) {
+	data, err := os.ReadFile(path)
+	if os.IsNotExist(err) {
+		return ZoneFile{}, nil
+	}
+	if err != nil {
+		return nil, fmt.Errorf("read zone file %q: %w", path, err)
+	}
+	var zf ZoneFile
+	if err := yaml.Unmarshal(data, &zf); err != nil {
+		return nil, fmt.Errorf("parse zone file %q: %w", path, err)
+	}
+	if zf == nil {
+		zf = ZoneFile{}
+	}
+	return zf, nil
+}
+
+// WriteZoneFile writes an OctoDNS YAML zone file, creating parent directories as needed.
+// yaml.v3 sorts map keys alphabetically, ensuring deterministic output.
+func WriteZoneFile(path string, zf ZoneFile) error {
+	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
+		return fmt.Errorf("create directory for zone file: %w", err)
+	}
+	data, err := yaml.Marshal(map[string]interface{}(zf))
+	if err != nil {
+		return fmt.Errorf("marshal zone file: %w", err)
+	}
+	if err := os.WriteFile(path, data, 0o644); err != nil {
+		return fmt.Errorf("write zone file %q: %w", path, err)
+	}
+	return nil
+}
+
+// BuildZoneFile constructs the desired zone file from the set of active subdomains.
+func BuildZoneFile(subdomains map[string]struct{}, cfg *Config) ZoneFile {
+	zf := make(ZoneFile, len(subdomains))
+	for sub := range subdomains {
+		zf[sub] = buildRecord(cfg)
+	}
+	return zf
+}
+
+// buildRecord creates the YAML-serialisable record value for a subdomain.
+// Returns a single-record map (OctoDNS simple syntax) when only IPv4 is configured,
+// or a two-element list (OctoDNS list syntax) when both A and AAAA are required.
+func buildRecord(cfg *Config) interface{} {
+	aRec := map[string]interface{}{
+		"ttl":    cfg.RecordTTL,
+		"type":   "A",
+		"values": []string{cfg.PublicIP},
+	}
+	if cfg.PublicIPv6 == "" {
+		return aRec
+	}
+	aaaaRec := map[string]interface{}{
+		"ttl":    cfg.RecordTTL,
+		"type":   "AAAA",
+		"values": []string{cfg.PublicIPv6},
+	}
+	return []interface{}{aRec, aaaaRec}
+}
+
+// DiffZoneFile computes the difference between the current (on-disk) and desired zone files.
+// It reports how many records were added, removed, or changed.
+func DiffZoneFile(current, desired ZoneFile) RecordStats {
+	var stats RecordStats
+	for k := range desired {
+		if _, exists := current[k]; !exists {
+			stats.Added++
+		}
+	}
+	for k := range current {
+		if _, exists := desired[k]; !exists {
+			stats.Removed++
+		}
+	}
+	// Detect value changes (e.g. IP or TTL updated in config).
+	for k, dv := range desired {
+		cv, exists := current[k]
+		if !exists {
+			continue
+		}
+		// Marshal both sides to compare: handles nested maps and slices uniformly.
+		cs, _ := yaml.Marshal(cv)
+		ds, _ := yaml.Marshal(dv)
+		if string(cs) != string(ds) {
+			stats.Changed++
+		}
+	}
+	return stats
+}
+
+// ZoneFilePath returns the absolute path to the dynamic zone YAML file for a given zone.
+func ZoneFilePath(cfg *Config, zone string) string {
+	return filepath.Join(cfg.RepoPath, cfg.DynamicDir, zone+".yaml")
+}